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UBC Theses and Dissertations

Solar ultraviolet radiation and outdoor workers in Canada : a program of research on exposure assessment, sun protection behaviours and prostate cancer risk Peters, Cheryl Elizabeth


Background: Exposure to solar ultraviolet radiation (UVR) is the main cause of skin cancer, and emerging evidence shows that it may prevent prostate cancer. Understanding the etiology of skin cancer has been challenged by a lack of detailed exposure assessment instruments, and this influences the ability to study the effect of solar radiation on other, more multi-factorial diseases. Methods: In the first study (Chapters 3 and 4), 78 outdoor workers wore UVR dosimetry badges for five work days, and provided information on skin cancer risk factors and sun protective behaviours. This data was used to investigate levels of exposure and prevention behaviours. The second study (Chapters 2 and 5) developed a job exposure matrix (JEM) based on occupation/industry, time spent outdoors and satellite data on available ambient UVR. The JEM was used to investigate the risk of prostate cancer in outdoor workers using a previously conducted population-based case-control study. Results: Over 300 UVR measurements were taken among seventy-three workers. Exposure was variable; the main predictors of exposure were time spent outdoors and meteorology. Outdoor workers relied more on clothing (hats, shirts) than on shade or sunscreen for protection. Sun protection scores showed that fairer people used more protection. The job sites’ clothing requirements also influenced protective behaviours. Based on the JEM, approximately 1.5 million Canadians (82% male) were exposed to solar UVR at work (for ≥2 hours/day). The largest exposed groups were construction workers, farmers and landscapers. Prostate cancer cases (n=1638) were compared to controls (n=1697) using the UVR satellite data-enhanced JEM and case status from national cancer registries. A statistically significant decrease in risk of prostate cancer was found in the highest exposed workers. Conclusions: Outdoor workers in Canada experience high levels of solar UVR exposure. Sun protection was relatively high and was driven by workplace requirements, which suggests company policies requiring hats and shirts could be an effective prevention strategy. JEMs are a key tool for population-level studies, and the addition of objective measures into the matrix for solar UV radiation was an innovation that showed high, long-term occupational exposure to solar UVR is protective for prostate cancer.

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Attribution-NonCommercial-NoDerivs 2.5 Canada